Recently, with the development of portable devices, smart phones, tablet computers, game machines, study assistance devices, and cameras have been widely used, and an input type of the devices has been developed from an existing mouse or keyboard to a touch type. Since the input type using a touch can directly select and control icons or programs on a screen while a user watches the screen, there are advantages in that the device may be decreased in size and reduced in weight and simultaneously, an intuitive use method is provided to a user.
A resistive type and a capacitive type have been the most widely used as the touch sensing type. Among the types, recently, the use range of a capacitive touch panel having a simplified configuration and high operational reliability has been most rapidly increased.
FIG. 1 is a configuration diagram of a capacitive touch panel in the related art. A touch sensor 10 has a structure in which a touch electrode 31, 32 is installed on a substrate 11, the touch electrode has a diamond shape, a driver electrode 31 and a sensor electrode 32 are positioned to cross each other, and an insulating layer 33 is formed between the driver electrode 31 and the sensor electrode 32. The electrodes are horizontally or vertically connected to each other and connected with an external driver circuit through a terminal part 22 and a signal line 20.
In order to determine a position where a human body touches, a predetermined signal is scanned to the driver electrode and the signal is transferred though capacitance formed between the electrodes. When the human body touches or is close to the touch sensor, a capacitance value formed between the electrodes is changed and thus the signal transferred between the electrodes is changed due to the capacitance value change. The position where the human body touches may be detected by detecting the change of the signal transferred to the sensor electrode, and a position touched on a 2D coordinate may be determined by comparing a time of applying a scanning signal with the detected electrode.
FIG. 2 schematically illustrates an operational principle of a capacitive touch sensor in the related art. As illustrated in FIG. 2, a circuit device connected to the driver electrode transmits a signal (mainly, a pulse signal) having a predetermined shape to the sensor electrode. Since the capacitance structurally formed between the two electrodes exists, an AC component of the pulse signal applied through the driver electrode may be transferred from the driver electrode to the sensor electrode. A value of the signal transferred without the touch of the human body is set as a reference point. When the human body touches while the signal is transferred through the driver electrode, the capacitance value between the driver electrode and the sensor electrode is changed. Since the human body operates as a load having capacitance, the signal detected from the sensor electrode is changed. When the change amount is detected, it may be determined whether the human body touches. The method is a principle of a structure of a general capacitive touch sensor.
FIG. 3A is an enlarged diagram of an A part of the capacitive touch sensor in FID. 1. FIG. 3B is a diagram schematically illustrating a cross section of a I-II section in FIG. 3A. Referring to FIG. 3A, a driver electrode 31 is configured as a transparent electrode by using ITO and crosses a sensor electrode 32. Two electrodes are positioned on different layers and a dielectric layer 33 of FIG. 3B is disposed between the two layers, and as a result, the two electrode layers are not short-circuited to each other.
In the structure, at least three layers including the insulating layer are required because a conductive electrode layer is stereoscopically configured with two layers. The more layers of the touch sensor mean the more number of processes in a manufacturing process. Further, since two electrode layers are not overlapped with each other on a vertical line with the insulating layer interposed there between, when an upper electrode and a lower electrode are manufactured, the upper electrode and the lower electrode need to be precisely aligned with each other in the manufacturing process. If an overlapping phenomenon occurs between the electrode layers, an electric problem does not occur, but when an image is transmitted only at the overlapped portion, transmittance is decreased, and as a result, a phenomenon such as spots occurs on the screen.